Hypoglycemia is defined as a blood glucose level that is approximately below 2.5. mM. Such low levels of glucose in the blood are mostly encountered in the course of treating diabetes, usually caused by excess insulin in either type 1 or increasingly type 2 diabetes. As the brain is so dependent on glucose, robust counterregulatory responses have evolved to sense hypoglycemia and restore normal blood glucose. Hypoglycemia is sensed by specialized glucose-sensing neurons in the ventromedial hypothalamus, which when activated send autonomic signals, especially to the adrenal glands to release epinephrine and to the pancreas to release glucagon. Unfortunately, these counterregulatory responses are often impaired in patients with diabetes, and this impairment is considered a major obstacle in the optimum treatment of diabetes. Counterregulatory impairments are caused largely by antecedent hypoglycemia. There are no currently approved treatments for counterregulatory failure, although the opioid antagonist naloxone shows some promise for this purpose.

Original languageEnglish
Title of host publicationEncyclopedia of the Neurological Sciences
PublisherElsevier Inc.
Number of pages2
ISBN (Electronic)9780123851574
ISBN (Print)9780123851581
StatePublished - 1 Jan 2014


  • Counterregulatory responses
  • Diabetes
  • Glucagon
  • Glycemia
  • Hyperglycemia
  • Insulin
  • Naloxone
  • Ventromedial hypothalamus


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